Friction-pivot



B. L'IEBOWITZ.

FRICTION PIVOT. APPLICATION FILED JULY 31,1919.

Patented July 27, 1920.

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FRICTION PIVOT. APPLICATION FILED JULY 31.1919. 1,348,020. Pate ted July27, 1920.

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IN V EN TOR. Ze/ynm/h Zhsawfz ATTORNE UNITED STATES T T Q BENJAMINLIEBOWITZ, on NEW OCHELLE, wim.

FRICTION-PIVOT.

Specification of Letters Patent.

Application filed July 31, 1919. Serial No. 814,558.

To all whom it may concern Be it knownthat I, BENJAMIN Lmnowrrz, acitizen of the United States, residing at the city of New Rochelle,county of Westchester, and State of New York, have invented certain newand useful Improvements in Friction-Pivots, of which: the following is aspecification.

My-invention relates to improvements in pivots of the type shown anddescribed in my Patent No..1,305,815, issued June 3, 1919, wherein Ihave disclosed a pivot for connecting two relatively movable parts whichare continuously maintained under load, in such manner as to producerolling contact between the pivot and its bearing for small angulardisplacements of the connected parts, and sliding. contactforlargerdisplacements.

. In said patent I have pointed out that the pivot is; particularlyapplicable to certain types of vehicle suspensions, such, forexample, asshown in my Patent No. 1240992, issued September 25th, 1917, and mycopending application, Serial No. 93,837, filed April 27th, 1916, andthat in such suspension it operates as a shock absorber, that is to say,it acts to quickly dampen the oscillations of the suspended body whenthey exceed a predetermined amplitude without introducing anyobjectionable friction for small displacements of the connected parts.

The object of my present invention is to separate the rolling andsliding functions of the pivot and to have them come on separatesurfaces, so that the'eurvature of the rolling surfaces will not beappreciably changed by wear.

I accomplish this result by introducing a floating bushing between thepin and the stationary bearing, as will be hereinafter explained andpointed out in the claims.

In the accompanying drawings illustrating my invention,

Figure 1 is a side elevation of one embodiment of my invention;

Fig. 2 is an end elevation of the same;

Fig. 3 is a section on the line 22 of Fig. 1; I 1 F ig. 4 is a sectionon the line 4-4. of

ig. 5 is a section of a modification;

Fig. 6 is an elevation of a vehicle suspension of the type described inmy co-pending application, Serial No. 93,837, showing the application ofmy present invention thereto; and, 7'

modified form of the pivots of Fig. 6.

.Referring to Figs. 1 to 4, inclusive, l is a steel bar 'or tube, whichacts as the pivot pin and to the ends of which the bell crank PatentedJ1i1 '27; 1920.

Figs..7 and 8 are two views showing a arms2 and 3 are'splined orfastened and suitable manner the bushings or bearings 6. Sliding freelyon these bushings are the floating bushings 7. The inside diameter ofthe bushing 7 is larger than the outside diameter of the pin 1. f Itwill be understood that the bell crank-arms are attached to parts (notshown), as for example, initially strained springs or-tension memberswhich operate tocontinuouslymaintain the pivot under load.

The action of the pivot is as follows:

'For small angular displacements, the only motion of the pivotis one inwhich thepivOt pin 1 rolls on the bushing 7. But in so doing the lineofcontact between the parts 1 and 7 travels around and thereby a slippingtendency is set up. Before this tendency has reached the point where thepin 1 will actually slide on the bushing 7, the said bushing will rotate(by sliding) in the bushing 6 so that the wear will come on the surfacesbetweenthe bushings 6 and 7 and not between' the bushing 7 and thepin 1. It is to be understood that the coefficient of friction betweenthe bushings 6 and 7 is smaller than that between the pin 1 and thebushing 7. To insure this, the bushing 6 may be made of bronze or othersuitable material, or the surfaces between the bushings 6 and 7 may belubricated, as by means of oil cup 11, without lubricating the surfacesbetween the 'pin 1 and the bushing 7. In general, how

allel lines on rolling surfaces, hence; sliding will occur more easilyon the lntended surfaces.

Ifjdesired, theco-efiicie'nt "of friction lo e tween the rollingsurfaces may be artificially raised, as, for example, by cutting fineparor on both.

Referring now to F ig. 6', which. shows my invention applied to asuspension of the character described in my co-pendingapplication,.Serial No. 93837, having an initially strained spring and a pair oftension members 21. In this construction the eyes 5 of the tensionmembers QItake the place of the casting 5 ofthe prec'eding figures. Theother partsof Fig. 6 arenumbered to correspond with likeparts :of thepreceding figures and will, therefore, be readily understood. s

Referring now to Figs. 7 and 8, which .s howa'modific'ation of thepivotsof Fig. 6,

1 v is the pivot pin and 7. is the bushing on which it rolls. Thebushing Ti's fastened in the eye 5 and, unlike the previous figures,does not slide therein. Instead, the pin 'floats on the bushing ,6 whichis fastened in theeye 5., 1 The only'difference between the action ofthis "pivot and thatshown in the preceding figuresv is that the slidingaction comes between the pin 1 and bushing 6,

and the rolling action between the :pin 1' and the bushing 7. Thisillustrates how the constructionof my pivotmay bemodifiedwith- .From theforegoing description it will be seen that my invention comprises twopivot-pairs, one adapted for-rolling and the other for sliding. Forsmall angles of rotation the motion of the pivot is a pure rolling ofthe rolling pivot-pair; for larger angles the motion is a sliding ofthesliding pair, the pivot being so arranged that no one of the rollingsurfaces N e ferential' contact with the other, whereby out departingfrom the spirit of my inv'en-- appreciable sliding will come on-therolling pivot-pair.

VVhat I claim is 1. In a friction pivot which is maintained continuouslyunder load the combination of, a bear1ng, a pivot-pm eccentric 1n thebearlng, and a bushing having tangential contact with one of the partsand circumtion, the other of said pivot-pairs being adapted for rollingmotion through a predetermined angle of rotation byhaving the innerelement of the rolling pair of smaller radius than the outer, the ratioof said radii being such as to cause sliding when said predeterminedangle has been exceeded.

. 3. In a friction pivot whichis maintained continuously under load, thecombination of a pivot pin, a bearing, and abushing, said. elementsconstituting two pivot-pairs, one of said pivot-pairs being adapted forrolling. motion through a predetermined angle of rotation by havingtheinner element of said pair of. smaller. radius than the outer, the ratioof the radii being such as 'to'cause a sliding tendency when saidpredetermined angle has'been exceeded, the other of said'pivot-pair'sbeing adapted for sliding 'motion whereby the sliding tendency set up inthe rolling pivot-pair will cause sliding rotation of the slidingpivot-pair, without causing any appreciable sliding in the rollingpivot-pair. V

BENJAMIN .L'IEBOWITZ.

